In the movie's opening, Josh Parker, played by Jason Bateman, is on the verge of completing his divorce proceedings while also navigating his demanding role as the Chief Technical Officer at an IT firm called Zenotek. Upon arriving at work, he encounters his eclectic group of coworkers, including Mary, the strict HR Administrator portrayed by Kate McKinnon, who often butts heads with her more carefree colleagues. Notably, there's the flamboyant Meghan (Jamie Chung), alongside the unpleasant Jeremy (Rob Corddry), and the heartbroken Alison (Vanessa Bayer), who's trying to move on after being cheated on. Meanwhile, Nate (Karan Soni) pretends to have a girlfriend to avoid the relentless teasing from his peers.
Josh soon meets up with his coworker and friend, Tracy Hughes, played by Olivia Munn, who is working on a cutting-edge software initiative for the company. They share a palpable chemistry, yet Josh remains too timid to express his feelings. Together with his manager, Clay Vanstone (portrayed by T.J. Miller), they head out to do some holiday shopping, where an amusing mishap occurs when Clay accidentally topples a Christmas tree in a department store.
As the office gears up for the festive season, Carol, the intimidating CEO known as "the Dragon Lady," played by Jennifer Aniston, bursts onto the scene, shutting down even the slightest hint of a holiday party. This is triggered by a startling dip in the company's sales, which has prompted Carol to consider closing branches, including theirs. In an effort to save their jobs, Josh, Clay, and Tracy scheme to impress a potential client, Walter Davis (Courtney B. Vance), by throwing a clandestine party, hoping it will showcase the vibrant culture at Zenotek.
As the night unfolds, chaos ensues at the party. Josh, determined to impress, engages in humorous antics, including an eggnog luge that inadvertently amplifies the night's madness. Alison and Fred's awkward romantic moment adds an unexpected twist when he begins to act like a child, causing her to flee. Meanwhile, Nate's secretive rendezvous involving an escort leads to further hilarity when he discovers the hefty price tag for her company.
Just as Walter shows signs of interest, the festive atmosphere spirals out of control, culminating in a series of breathtaking misadventures that put Josh, Clay, and their jobs at risk. After a thrilling car chase to stop Clay from making a risky stunt, the events of the night culminate in a dramatic crash that causes a citywide internet outage.
With their backs against the wall, Josh, Tracy, and Mary rally together to resolve the crisis, leveraging Tracy's innovative program to restore internet services, ultimately securing their jobs as they receive a much-needed lifeline from Walter. In the aftermath, romantic sparks fly between Josh and Tracy as well as Nate and Alison, leading to a heartwarming conclusion where even Clay and Carol find common ground amidst their professional rivalry.
The film culminates in a lighthearted breakfast gathering at the hospital, where, despite the doctor's warnings, they plan to indulge in some holiday cheer, showcasing the joy and camaraderie that ties them all together.
